Joe Perez

iTrader: (8)

Pretty much. You should read the MS-II specific documentation here: http://www.megamanual.com/ms2/index.htm with particular attention to the "Installation" section- there is one jumper you need to add to the main board that MS-I does not require. And as Briney said, some of the "advanced" I/O gets pinned out differently.

The "big deal" with the MS-II in this regard isn't so much any additional capability or feature related to the extra processing power so much as the fact that the MS-II config software happens to natively support the NB's rather unusual crank wheel and cam setup, whereas there doesn't seem to be a way to configure the MS-I's software to deal with those inputs.

maharashii

Sweet. Consider me interested. PM me when you're closer to doing so, and I'll do the same before I start ordering BEGI-S parts.

For my parallel install, looks like I have to choose:

1. MS-I on PCB v3.0 with NA CAS (a la Braineac)
2. MS-II on PCB v3.0 with stock NB CAS (a la AbeFM)

The first option has been done by quite a few on this board, while the last one seems to have only been done by Abe, but should be an easier install since I don't have to funk with the CAS, but then I end up getting awfully close to the leading edge. In other words, if the **** hits the fan, I'll have to drive to San Diego and drink Joe's beer while he fixes it for me

Would my decision on which way to go be influenced at all by whether or not I bolted my '99 head to a '94-97 block or a '99-00 block? I'm still shopping for a 1.8L short block, and I'm not sure what I will end up with just yet.

Joe Perez

iTrader: (8)

No, no, no... You drive to San Diego and drink Abe's beer, while Joe laughs.

It's hard for me to know what factors would influence your decision. Personally, I'd be strongly influenced by the offer of a three-way with Tricia Helfer and Grace Park, but if bolting engine parts together is your thing...

Seriously, it doesn't matter one bit which block you are running so long as the head is an NB part and the block has the crankwheel sensor mounting hole (I don't know if the '94-'95 blocks do.) The sensors and factory harness are what drive this decision. Either you choose to use the stock NB stuff, or you choose to install a CAS, run additional wiring, and live with spark jitter. I do know that the '96-'97 crank sensor and the NB crank sensor are mechanically different, but electrically they should be the same. (It's possible that their alignment is different, so you'd probably want to stock with the NB sensor)

I don't think Abe's the only one. The whole reason the MS-II is "special" insofar as the NB is concerned is that it comes pre-loaded with a decoder for the NB crank and cam sensors- you literally just select "NB" from a drop-down menu and the decoder is ready to go. Therefore I have to assume that others have gone before. (Granted, Abe seems to have been one of the principle driving forces behind getting James & Phil to make this change to the software)

Marc D

iTrader: (7)

wow no ****! Thats great if the only needed choice is to just select the NB from a drop-down menu. I havent checked the actual setup of trying see the megatune settings for MSII.

what my original question was implying was if there is a special schematics that is required to make the stock sensors work properly (i.e. external box with a bunch of resistors and caps or what not)

so all in all, all you need to do now is just hook up the wires from the stock cam sensor and crank sensor to the inputs on the stock NB? and mod the MSII accordingly?

Joe Perez

iTrader: (8)

I only looked into it recently myself. Despite their common heritage, the software configuration for MS1 and MS2 differs greatly in many ways.

With the MS1, for example, in order to change your CLT and IAT sensor values, you must re-flash the whole firmware, which requires you to disconnect the ignition system, compile code (well, not compile exactly since it's ML to begin with) then re-load your MSQ, basically a lot of ******* around. With MS2, you just enter a couple of numbers into a screen.

Likewise, the MS2 seems to come with a lot of common wheel setups already defined in a drop-down menu. With MS1 you have to calculate and then manually enter the tooth configs for your wheel. It's not hard and it's a one-time deal, but it's just different.

On the other hand, there are some things with MS1 that are easier. As far as I know, MS2 does not have a working closed-loop idle, so in a standalone configuration you have to fiddle around with duty cycles and such. With MS1, you just enter a couple of target RPM values and some DC limits, and it auto-seeks the idle you've told it to.

The input hardware is the same for MS1 and MS2. Either way you've got to build a second trigger input and, if necessary, a filter circuit to clean up the primary. For most people, this does not seem to require a lot of complexity, just a couple of resistors and a cap. In my case, dealing with my CAS (which I believe to have simply been marginal) was a living nightmare- hence my crankwheel project.

cjernigan

iTrader: (13)

Arga was the first MS2 parallel install on an NB. Pretty sure he is the one that got the guys to write up the beta code to use the NB sensors.
I'm running MSI with a 94-97 CAS and it works great. The install is easy and i don't have issues with it running correctly. Grounding is very important and so is the rest of your wiring.

It might be more accurate to use the NB sensors but considering there are only two people running parallel MS2 on an NB i believe and one of them is now going standalone I would suggest you go MSI V3.0 is parallel.

I truthfully think MSI with a crank trigger like Joes is the way to go for sure unless a circuit can be built to use the NB sensors.

Or there is always Joes idea of grinding the odd spaced teeth off the NB wheel and using it as a two tooth wheel.

patsmx5

iTrader: (16)

I was MSII parallel on my 99 for a few months. I had some problems with my MS and wiring harness and have decided to go standalone now for simplicity. I will be using a Ford EDIS 4 ignition system with my MS2 for ignition though. It's simple and well engineered, but would require you to fabricate the parts to mount the trigger wheel and sensor. Should be a bit better than the stock stuff, simpler, and more accurate. Plus I won't have to deal with hooking and unhooking my coils anymore.

I will say though you can run MS2 on stock sensors, I did it. You need two simple circuits in the MS for ignition inputs. They are really simple. PM Arga and ask him to send you the diagrams for them. They are the same for cam and crank sensors. Do that, select NB, and it works.

maharashii

what's "spark jitter"? I searched but didn't find much.

Joe Perez

iTrader: (8)

Jitter, in general, is the tendency of an electrical signal to exhibit small and usually random deviations from "normal" in the temporal domain.

Translated into English, that means that if you set the spark to 10°BTDC and rev up the engine, it might be jumping around between 7° and 13° (or more).

It tends to happen at higher RPM, and its caused by the fact that the CAS is driven by the timing belt. That belt, by design, has a small amount of slack in it, and thus the CAS is not perfectly locked to the crank- it wanders around a bit.

By moving to a crankwheel, this variable is eliminated.

ZX-Tex

iTrader: (15)

Hey I understand the phenomenon here, but is the error really that high? On the order of +/- 3 degs?

Joe Perez

iTrader: (8)

Yes. While I was testing an ignition input circuit, I locked my timing at 10° and slowly revved the engine from idle to about 6k while observing the timing mark. I was actually looking for drift (due to input latency) but saw an amazing amount of jitter as well.

Before anyone asks, my timing belt is about 3 years old, has ~15k miles on it, and was properly tensioned.

maharashii

Ahh, this is becoming clearer now. I think I was partly confused because people seem to use CAS interchangeably to refer to the crank sensor or the cam sensor. When I hear CAS, I am thinking of the NA optical cam sensor. Is that right?

Are these statements correct?

• NA 1.8L has an optical CAS that can lead to jitter
• NB 1.8L has a magnetic crankwheel sensor that is more accurate
• MS-I uses the optical CAS for timing input
• MS-II uses the magnetic crankwheel for timing input

In my case, as I'm looking for a block, I can use the following combinations (no matter what I will use my '99 head):

1. Stock ECU with NA block and NA optical CAS
2. MS-I with NA block and NA optical CAS
3. MS-I with NB block and NA optical CAS
4. MS-II with NA block and NB magnetic crank wheel (need to verify compatibility with block)
5. MS-II with NB block and NB magnetic crank wheel

Questions:

1. Does the NB have any sort of cam sensor, or just the crankwheel sensor?
2. Does the NA have any sort of crankwheel sensor, or just the optical CAS?

I'm trying to decide if I will swap the block and get it sorted out with the stock ECU, or Megasquirt the car now and swap in whatever block I find in the future.

ZX-Tex

iTrader: (15)

Wow, OK thanks for the info.

Joe Perez

iTrader: (8)

Yes. Usually, CAS refers to the sensor which plugs into the back of the camshaft on the NA, is either optical or hall-effect, and provides two discrete open-collector outputs: CMP (one pulse per crank rev) and CKP (two pulses per crank rev, aka 1 pulse per ignition event)

I'm not sure if there is a common convention for describing the two sensors (crank and cam) on the NB, or for distinguishing the crank sensor on the late NA from the CAS.

Understand that ALL miatas from '89-'05 have two trigger signals, one which gives one pulse per ignition event (two pulses per crank rev) and the other which gives one pulse per crank rev. The locations of these sensors has moved around over the years, as follows:


All NAs use a camshaft-driven CAS, be it optical or hall, for the primary trigger input and the TDC input. This is prone to jitter due to the loose coupling of the cams to the crank. This CAS provides both the crank reference and the cam reference.

Starting in '96, NAs were equipped with a crankwheel with four oddly-spaced teeth, for the sole purpose of OBD-II misfire detection. They still have the same two-channel CAS as the earlier cars, and with the stock ECU, they use it for the primary triggers. The crankwheel is basically the same as the one fitted to NBs, although the sensor is physically different. (the mounting point changed)

Starting in '99, the crankwheel was used as the primary trigger input, the CAS was eliminated, and a simpler, single-channel cam sensor was implemented to provide the "TDC" signal. Note that jitter in the cam reference is not critical, as this signal is used only to give the ECU a reference as to which crank pulse is which.

MS-I can use any of the following for timing input:
1- Both channels (CMP and CKP) of the stock NA CAS. This scheme requires adding a CAS to NBs, and provides low accuracy.
2- The crankwheel sensor (with two teeth cut off the wheel) of the '96+, and the CMP output of the NA CAS. This scheme requires adding a CAS to NBs, and is not compatible with parallel operation on any car since it requires cutting two teeth off the crank wheel.
3- (theoretical) the stock crankwheel of the NB (with two teeth cut off) plus the stock camwheel of the NB (with the dobuletooth cut down to a single tooth.)
4- A single, crank-mounted wheel such as a 36-1, with a dedicated VR sensor. This scheme requires mounting a custom timing wheel.

MS-II can do all of the above, plus:
5- The stock crankwheel and camwheel of the NB, without physical modification to either.

Basically, what it boils down to is that the MS-1 requires all teeth to be evenly spaced, while the MS-2 does not.


1- Yes. It's near the front of the intake cam. It gives a very strange signal- one pulse at #1 TDC, and then two quick pulses 360 crank degrees later at #4 TDC. This is why it's unusable with MS-I, the software to deal with the single-double-single-double doesn't exist.
2- Yes, starting in '96.

Here is some further info on the NB wheels: http://www.msextra.com/ms2extra/MS2-Extra_Miata.htm I'm not sure why it says '99-'00 only, it's possible that the wheels changed in '01. I only have parts catalogs and docs going up to '99.

maharashii

Thanks for all the info. This makes much more sense now.

So how much trouble does that jitter cause? I see a lot of references to folks using the NA CAS with an MS-I on an NB, but this is the first I've read about jitter. +/- 3 degrees sounds like a lot.

My power goals are pretty moderate so I don't imagine I'll be living on the edge for tuning. Even if I get the urge to go higher than 180-200rwhp, I probably wouldn't do it. This is my dd and I have to be able to start from a stoplight on cold, wet, steep Seattle hills without looking like a wheel-spinning idiot.

cjernigan

iTrader: (13)

Even if you tune your car for 20 psi on a T04E you won't be making that HP off idle when taking off up a hill. I only spin my tires if i want to.

maharashii

I dunno - I'm skeptical. On a bad day (stopped on a really steep hill, with some ******* right on my bumper, on a cold wet day) I have a hard time launching with stock power. I suspect even a moderate increase in torque is going to be a challenge, but I digress ...

If I go with an MS-I and a parallel install, I do I need the IAT mod or can I just use the stock AFM/MAF?

Joe Perez

iTrader: (8)

It would, except that a reasonably-sized turbo isn't going to be adding any torque at that point. Not enough RPM, not enough throttle, not enough flow. Now, if you floor it while cruising along in 3'rd on that same cold, rainy day, then yes, your car is going to start sliding sideways.

Digressing a bit, but I find it helpful (when starting off uphill) to hold the e-brake up with my right hand while modulating the clutch and throttle, letting the brake out slowly as the clutch engages. Much easier to do gently than heel-toe.

In a turbocharged car, having the open-element GM IAT sensor will be beneficial beyond mere AFM/MAF removal, as it will allow to to read actual intake temp after the turbo and I/C.

ZX-Tex

iTrader: (15)

+1, works great.

Marc D

iTrader: (7)

i just read through the manual, still trying to comprehend those circuits. seems to be more complicated than i expected? or is it shown in excess on where exactly the signal is going through?

EDIT: examining more, it seems like some circuits will be needed to changed out of the original holes on the PCB board? for the CAM sensor, i understand that the circuit shown requires to be built using the listen components. the crank sensors input has my head spinning